fix error message

Signed-off-by: SungJin1212 <tjdwls1201@gmail.com>

Author: SungJin1212

integration/remote_write_v2_test.go

@@ -194,7 +194,7 @@ func TestIngest_SenderSendPRW2_DistributorNotAllowPRW2(t *testing.T) {
 	symbols1, series, _ := e2e.GenerateSeriesV2("test_series", now, prompb.Label{Name: "job", Value: "test"}, prompb.Label{Name: "foo", Value: "bar"})
 	_, err = c.PushV2(symbols1, series)
 	require.Error(t, err)
-	require.Contains(t, err.Error(), "server returned HTTP status 415 Unsupported Media Type: Remote Write V2 is disabled")
+	require.Contains(t, err.Error(), "io.prometheus.write.v2.Request protobuf message is not accepted by this server; only accepts prometheus.WriteRequest")
 
 	// sample
 	result, err := c.Query("test_series", now)

pkg/util/push/push.go

@@ -170,7 +170,8 @@ func Handler(remoteWrite2Enabled bool, maxRecvMsgSize int, overrides *validation
 			handlePRW1()
 		case remote.WriteV2MessageType:
 			if !remoteWrite2Enabled {
-				http.Error(w, "Remote Write V2 is disabled", http.StatusUnsupportedMediaType)
+				errMsg := fmt.Sprintf("%v protobuf message is not accepted by this server; only accepts %v", msgType, remote.WriteV1MessageType)
+				http.Error(w, errMsg, http.StatusUnsupportedMediaType)
 				return
 			}
 			handlePRW2()